What is the meaning of largeish in below text:
I'd like to book a largeish group of students from York High School into the barns for a few nights in July.
It's an informal way to say large, but not very large.
The -ish suffix is often used to mean "somewhat", "almost", "approximately", or "similar to". Note that although there are some accepted adjectives ending in -ish (e.g., mannish and greenish), the use of -ish as a hedge for quantities is generally too informal for writing.
It depends on what the author means by "a large group of students".
The suffix "ish" means "like" or "roughly" or "about". It is used to create adjectives. This particular use of "ish" is informal.
So if the author thinks 5 students constitute "a large group of students", then the meaning might be 3 - 7 students. If the author thinks 50 students constitute "a large group of students", then the meaning might be 30 - 75 students. If the author thinks 500 students constitute a "large group of students", then the meaning might be 200 - 1000 students, et cetera.